In the manufacture of multilayered semiconductor devices, a porous low dielectric constant film is used to reduce the parasitic capacitance of an interlayer insulating film in order to increase operation speed. An example of the porous low dielectric constant film may include a SiOC film containing silicon, carbon, oxygen and hydrogen and having Si—C bonds. The SiOC film is etched by, for example, plasma of a CF4 gas, which is a CF-based gas, using a resist mask and a lower layer mask in order to fill the SiOC film with a wiring material such as copper, and then the resist mask is ashed by plasma of an oxygen gas.
In addition, when the SiOC film is subjected to a plasma treatment such as etching or ashing, in an exposed surface of the SiOC film exposed to the plasma, namely a side wall and a bottom surface of a concave portion of the film, for example, some Si—C bonds are broken and C is desorbed from the film due to the plasma. Si with an unsaturated bond generated by the desorption of C is unstable as it is. As such, Si is bonded to moisture or the like in the atmosphere to become Si—OH.
In this way, a damaged layer may be formed on the exposed surface of the SiOC film by the plasma treatment. Such a damaged layer has a low content of carbon, which decreases the dielectric constant. As the line width of a wiring pattern becomes smaller and smaller and a wiring layer, an insulating film and the like become thinner and thinner, the proportion of the effect of a surface portion on the whole wafer W, which may be a factor that causes the characteristics of a semiconductor device to deviate from a design value due to the decrease in dielectric constant, becomes larger and larger.
Techniques have been proposed which includes: filling hole portions of a porous low dielectric constant film formed on a substrate with PMMA (acrylic resin) in advance; performing a treatment such as etching with respect to the low dielectric constant film; heating the substrate; supplying a solvent onto the substrate; applying a microwave to the substrate; and removing the PMMA. However, in order to remove the PMMA, it is necessary to maintain plasma for about 20 minutes and to heat the substrate up to a temperature of 400 degrees C. or more, which may cause a problem that it is highly likely to have an adverse effect on elements already formed on the substrate.